Active noise reduction (ANR) is a method to reduce ambient noise by producing a noise cancellation signal with at least one loudspeaker such that the undesired ambient noise perceived by the user is reduced. Reducing the amount of ambient noise may enhance the ear comfort and may improve the music listening experience and the perceived speech intelligibility, e.g. when used in combination with voice communication.
In active noise reduction, one or more microphones generate a noise reference (a reference of the ambient noise) and a loudspeaker produces a noise cancellation signal in the form of anti-noise which at least partially cancels the ambient noise such that the level of ambient noise perceived by a user is reduced or eliminated. The case of active noise reduction should be distinguished from sound capture noise reduction, where a noisy recorded microphone signal, e.g. for voice communication, is cleaned up. In other words, while active noise reduction improves the sound quality for the near-end user only, sound capture noise reduction improves the sound quality for the far-end user only. A further distinguishing feature is, that in active noise reduction the microphone generates a noise reference signal corresponding to the ambient noise which is to be reduced or eliminated, whereas the microphone in sound capture noise reduction is provided for recording a user signal of interest.
WO 2007/038922 discloses a system for providing a reduction of audible noise perception for a human user which is based on the psychoacoustic masking effect, i.e. on the effect that a sound due to another sound may become partially or completely inaudible. The psychoacoustic masking effect is used to reduce or even eliminate the human perception of an auditory noise by providing a masking sound to the human user, where the intensity of an input signal, such as music or another entertainment signal, is adjusted based on the intensity of the auditory noise by applying existing knowledge about the properties of the human auditory perception and is provided to the human user as a masking sound signal, so that the masking sound elevates the human auditory perception threshold for at least some of the noise signal, whereby the user's perception of that part of the noise signal is reduced or eliminated.
However, increasing the intensity of an input signal may lead to a distortion of the input signal.
In view of the described situation, there exists a need for an improved technique that enables for active noise reduction with improved characteristics, while substantially avoiding or at least reducing some or more of the above-identified problems.